Calcium ion has been known as an intracellular messenger for signal transduction, and it is suggested that various physiological events are triggered by the elevation of intracellular calcium concentration. Calcium influx from extracellular fluid is one of the mechanisms for the elevation of intracellular calcium concentration. The gate of calcium influx is the voltage-dependent calcium channels. The voltage-dependent calcium channel is opened by the polarization of plasma membrane, and calcium ion influxes from extracellular fluid into the cell selectively through the channel according to the electrochemical gradient. The voltage-dependent calcium channels are classified into N-, L-, P-, Q- and T-type at present. It is known that L- and T-type calcium channels are distributed in the various tissues ubiquitously, and especially, L-type calcium channel is enriched in the smooth muscle cells or the cardiac muscle cells. On the other hand, N- and P-type calcium channels are mainly located in the nervous system and related to the neurotransmitter release. This neurotransmitter is stored in synaptic vesicles of nerve terminals at resting state. When action potential by signal transmission on nerve is conducted in pre-synaptic fiber and reaches to the nerve terminal, the voltage-dependent calcium channels are activated and then, calcium ion influxes into the nerve terminals. By these mechanisms, synaptic vesicles are fused with pre-synaptic membrane, and neurotransmitters in the vesicles are released. The released neurotransmitters are related to signal transmission in synapse due to binding to their receptors in post-synaptic membrane. From the above, an N-type calcium channel blocker is thought to be effective on various diseases induced by an excessive release of neurotransmitter. For example, it may be useful as agent for the prevention and/or treatment of cerebral infarct (J. Cereb. Blood Flow Metab., Vol. 17, 421-429, 1997), transient ischemic attack, encephalomyelopathy after cardiac operation, spinal angiopathy, hypertension with stress (Science., 239, 57-61, 1988), neurosis, epilepsy, asthma and pollakiuria etc. or agent for the treatment of pain (for example, acute pain, chronic pain, pain after operation, cancer pain, neuralgia, pain caused by infection etc.) (Pain, 60, 83-90, 1995).
The venoms isolated from the genus Conus, ω-conotoxin GVIA, MVIIA, are well known as N-type calcium channel blockers.
But, these ω-conotoxins are peptide compounds, so it is expected that they have various problems (for example, they are not absorbed into the living body easily). Therefore, there is a demand for arrangement of these blockers to non-peptide compounds namely to small-molecule. There are some reports relate to small-molecule as follows:
For example, it is described in the specification of Japanese Patent Kokai Hei 8-217671 that glycine derivatives of the formula (A)R1ACH(OCOR2A)CH2CONHCH2CO2H  (A)(wherein R1A and R2A are, same or different, C1-19 straight or branched alkyl or C2-19 straight or branched alkenyl) and salts thereof are N-type calcium channel blocker.
It is described in the specification of EP 805147 that the compounds of the formula (B) (wherein R1B is alkyl, R2B is hydrogen, optionally substituted alkyl, optionally substituted aryl or optionally substituted heteroaryl, R3B is hydrogen, CN, XB is bond or SO2, R4B, R5B, R6B, R8B, R9B and R10B are each hydrogen or alkyl, AB is CH2 or YBCO (in which YB is bond), R7B is C α-substituent of amino acid or ester thereof, R6B and R7B together form C3-5 alkylene chain optionally substituted by C1-4 alkyl or hydroxy or CH2—ZB—CH2 (in which ZB is CO, S, SO, SO2), R7B and R8B together form C3-5 alkylene chain optionally substituted by C1-4 alkyl or hydroxy, BB is CON(R21B), mB is 0˜2, R11B is hydrogen or alkyl, R12B is hydrogen, alkyl, optionally substituted aryl or optionally substituted heteroaryl, R13B is alkyl, optionally substituted aryl or optionally substituted heteroaryl, R12B and R13B together form C3-8 cycloalkyl), the salts thereof or the ester thereof are calcium channel modulator (necessary part is extracted in the explanation of the group).
Also, it is described in the specification of Japanese Patent Kokai Sho 61-200950 that the compound of the formula (C) (wherein RC and R1C each independently, is lower alkyl, aryl-lower alkyl or phenyl optionally substituted by one or more electron-withdrawing or electron-donating group, R2C and R3C each independently, is hydrogen, lower alkyl, aryl-lower alkyl or phenyl optionally substituted with one or more electron-withdrawing or electron-donating group, and nC is 1˜4) and pharmaceutically acceptable salts thereof are anti-convulsant agent.
In addition, the present inventors (applicant(s)) have filed two international applications relating to an N-type calcium channel inhibitor (WO99/02146 and international application No. PCT/99/03409 (filing date: Jun. 25, 1999)).
Further, as for an application relating to an N-type calcium channel inhibitor, WO98/54123 is listed.
Besides the above applications, WO 99/25686 (cyclic amine derivatives possessing inhibitory action on chemokine) is listed.